Possibly the single coolest combat vehicle in the "Star Wars" universe, Imperial Walkers, or AT-ATs (All Terrain Armored Transport), are used by Imperial ground forces to crush enemy resistance and morale. At the infamous Battle of Hoth, AT-ATs proved to be the decisive weapon in breaking Rebel defenses, and gave the original trilogy one of its signature set pieces.
Legend holds that George Lucas' inspiration for the Imperial Walker came from giant cargo lifters on the San Francisco Bay -- although this origin story has apparently been refuted by the the man himself. In any case, subsequent details gradually emerged in the "Star Wars" canon: AT-ATs stood 22.5 meters high and were powered by massive hydraulic joints using compact fusion drive engines.
In the realm of contemporary robotics, Boston Dynamics' BigDog robot (inset) is similar in style, if not scale, to those massive Imperial Walkers. About the size of a small mule, the BigDog uses a hydraulic actuation system to power four articulated legs designed to navigate rough terrains. BigDog can run, climb slopes and carry more than 300 pounds of cargo.